This specification relates to composite image formation.
Image capture devices, such as cameras, can be used to capture an image of a section of a view, such as a section of a landscape. The section of the view whose image is captured by a camera is known as the field of view of the camera. Adjusting a lens associated with a camera may increase the field of view. However, there is a limit beyond which the field of view of the camera cannot be increased without compromising the quality or resolution of the captured image. It is sometimes necessary to capture an image of a view that is larger than can be captured within the field of view of a camera. To do so, multiple overlapping images of segments of the view can be taken and then the images can be joined together (e.g., merged) to form a composite image, e.g., as a panoramic or a mosaic image.
To form a composite image, the relative positions of the component images representing adjacent sections of the view must be determined. In some systems, two component images are aligned. Additional component images are aligned with respect to the first two component images. Images can be aligned for example, using camera properties, e.g., focal length, as well as image information, e.g., pixel data. One technique for aligning images is described in U.S. Pat. No. 7,103,236, which is incorporated by reference.
One technique for forming a composite image from aligned component images projects the images onto a circular cylinder, i.e., generates a “cylindrical projection”. A focal length and rotation angles associated with each image can be used to map the image onto a cylinder. For example, the orientation of the camera can be represented as a set of rotation angles from a reference orientation. The cylindrically mapped component images have less distortion than images mapped directly onto a plane. The cylinder can be unwrapped to derive a planar composite image, to print the composite image, for example. A description of using cylindrical projections to form a composite image is found in U.S. Pat. No. 7,006,707, which is incorporated by reference.
The composite image is often further processed to blend the seams of the overlapping component images. For example, pixel values along the seams of the overlapping component images can be modified to provide a smooth transition between the images.